Effects of Oxygen on In-vitro Biofilm Formation and Antimicrobial Resistance of Pseudomonas aeruginosae

Pseudomonas aeruginosa is an opportunistic human pathogen. This organism is thought to persist by forming biofilm within human infections. Bacteria growing in biofilm exhibits increased resistance to antimicrobial agents. In this study, we examined the effect of oxygen on the development of biofilm by P. aeruginosa and on the level of its resistance to the antibiotics. The P. aeruginosa control strain group and 45 clinical isolates were cultured and antibiotic susceptibility testing was performed by disk diffusion agar testing. Biofilm formations were examined by glass tube assay and were incubated at 37°C under normoxia (21% oxygen) and hypoxia (1% oxygen). We observed that hypoxia affects the biofilm formation under hypoxic conditions as compared to normoxia. Among the antibiotics tested, penicillin, cephalosporin and carbapnem, all demonstrated decreased susceptibility values under hypoxia compared to normoxia. We established that hypoxia induced biofilm formation; this suggests that decreased oxygen may be a critical factor in the bacterial virulence. Moreover, we confirmed a strong positive correlation between hypoxia and antimicrobial resistance of P. aeruginosa.